An amplifying circuit includes a first gain adjusting circuit, a second gain adjusting circuit, a load circuit and a switch module. When the amplifying circuit operates in a first mode, the first gain adjusting circuit receives a first input signal, and generates a first output signal to a second output terminal of the amplifying circuit via the load circuit and the switch module; and when the amplifying circuit operates in a second mode, the second gain adjusting circuit receives a second input signal, and generates a second output signal to a first output terminal of the amplifying circuit via the load circuit and the switch module.